Cellular communications systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular telephones allow users to place and receive voice calls most anywhere they travel. Moreover, as cellular telephone technology has increased, so too has the functionality of cellular devices and the different types of devices available to users. For example, many cellular devices now incorporate personal digital assistant (PDA) features such as calendars, address books, task lists, etc. Moreover, such multi-function devices may also allow users to wirelessly send and receive electronic mail (email) messages and access the Internet via a cellular network and/or a wireless local area network (WLAN), for example.
Even so, as the functionality of cellular communications devices continues to increase, so too does the demand for smaller devices which are easier and more convenient for users to carry. One challenge this poses for cellular device manufacturers is designing antennas that provide desired operating characteristics within the relatively limited amount of space available for the antenna.
One exemplary cellular antenna structure is disclosed in U.S. Pat. No. 6,897,817 to Jo et al. The antenna includes a conductive top plate formed in the shape of a spiral. In one embodiment a sidewall meanderline extends from an edge of the top plate in the direction of a ground plane. A shorting meanderline connects the top plate and the ground plane. A first region of the top plate overlies the ground plane. A second region of the top plate extends beyond the ground plane. Tuning is provided by adjusting the length and other dimensions of the meanderlines.
For internal antennas such as the one described above which are carried within the housing of a cellular device, it is typically difficult for such devices to comply with applicable specific absorption rate (SAR) and hearing aid compatibility (HAC) requirements due in part to the relatively close proximity of the antenna to the user's ear. As such, further improvements may be desirable to help achieve desired SAR and/or HAC requirements.